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Blue sky thinking

Header Image

Tom Ravenscroft

What: Tensile membrane structure Where: EUR, Rome

Over 24,000m² of perforated Atex 2000 TRL WS14 silicon membrane was used to form the cloud.
Over 24,000m² of perforated Atex 2000 TRL WS14 silicon membrane was used to form the cloud. Credit: Moreno Maggi

It’s not often a conference centre receives extensive coverage in the architectural press. Most are glorified sheds filled with halls and theatres, resulting in a bland, emotionless airport-like feel. But in Rome, using stressed fabric, Studio Fuksas has taken a different route.  

At the €353 million EUR convention centre, reportedly the largest building completed in the Italian capital in the past 50 years, Fuksas has turned its back on bland and created a fascinating combination of spaces. While externally it is rational – a smart glazed box – internally it is almost filled with an amorphous cloud-like form.

This 129m long, 65m wide, 29m high white cloud is the heart of the building. Inside is the centre’s main auditorium with approximately 1,800 seats, various large conference rooms with around 6,500 seats, foyer areas and a café. 

Envisaged by the architect as floating freely, its sinuous form contrasts directly with the geo­metrically defined shape of the exterior shell. However, to achieve this complex cloud, which was key to the architect’s vision, would push the capabilities of stressed fabric to its limits. 

Supported laterally by the building’s external frame, the cloud is a steel rib structure covered by a 14,400m2 transparent curtain. 

The shape of the steel frame was developed by virtually cutting the cloud form in all three axes at firmly defined distances into slices. These shapes were then manufactured in steel – creating a grid that the membrane had to be custom patterned to fit. 

  • 55,000m² of glass was used to cover the Congress building –equivalent in area to nearly eight football pitches.
    55,000m² of glass was used to cover the Congress building –equivalent in area to nearly eight football pitches. Credit: Moreno Maggi
  • Creating the €353 million Palace of Congress required over 39,000 tonnes of steel.
    Creating the €353 million Palace of Congress required over 39,000 tonnes of steel. Credit: Moreno Maggi

As the cloud’s primary steel structure was established first, the key engineering challenge was to design a stressed fabric form that followed the steel works’ multiple curvatures and complex shape as closely as possible. 

To do this, the architect turned to formTL, a German engineer that specialises in membrane facades and structures. 

As the cloud is indoors and not exposed to the elements it doesn’t have to meet more onerous performance requirements. This allowed the engineer to chose a semi-transparent white membrane material that would give the acoustic and visual requirements the architect desired. The material itself is constructed from glass fibre coated silicone Atex textile (Atex 2000 TRL WS14), manufactured by Valmiera Glass UK. To achieve the flexibility required to create the form and give the desired level of transparency this material was punched with millions of micro holes.

As Christian Würfl, senior engineer at formTL, explains: ‘It’s the most complex form we have ever undertaken; the combination of the extreme curves and their closeness makes this an extremely difficult shape to realise.’


Through what formTL’s Christian Würfl describes as a semi-manual form-finding process using 3D modelling, curvatures and stress ratios were determined along with a cutting pattern that maintained tension and distortion. A 1-1 mock up of the most complex section – the mouth of the tube – was also made. 

The membrane covering the steel framework uses 2,763 cutting patterns assembled into 607 individual panels. To maintain the levels of tension required of the membranes for each curvature a specific bracket system was developed. Each bracket is mounted on the steel ribs and is height-adjustable so they can be finely tuned to ensure the ribs do not collide with the skin and the membrane appears taught. The glass fabric is attached and tensioned using clamping lines that sit on the brackets.



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